1. Field of the Invention
The present invention relates generally to ink jet printers, and, more particularly, the invention pertains to an ink delivery system for use in an ink jet printer.
2. Description of the Related Art
Ink jet printers are used commonly in offices and home printing applications. Ink jet printers are popular due to their low cost of operation, low energy use and quiet operating features. Ink jet printing involves the ejection of tiny ink droplets through small holes, in a controlled manner, to create the desired image on the media intended to receive the image. Ink is supplied from an ink reservoir to a printhead, which includes various passageways from the reservoir to a plurality of firing chambers having nozzle orifices. Energy is applied to the ink from an ink droplet generator near each orifice, which may include the application of electrostatic attraction, the application of oscillating forces from piezo elements, the application of heat from heating elements or the like.
It is known to provide the nozzle orifices in a printhead cartridge that is mounted on a carriage that may support one or more such printheads. The carriage traverses back and forth across the medium being printed, and ink droplets are emitted as the carriage moves. One of the ways in which ink jet printing can be made faster is simply to move the carriage faster as the ink droplets are emitted. In doing so, it is desirable to minimize the amount of ink contained within the cartridge carried on the carriage, to reduce the weight and thus the momentum of the carriage. Further, the repeated and abrupt reversal in movement direction of the carriage traversing back and forth across the media can create turbulence in the ink, which in turn can cause printing problems due to air absorption, ink foaming and the like.
For some large printing devices, such as plotters used to create drawings, posters or other large printing jobs; or for printers such as color printers and printers designed for high volume print service utilizing large volumes of ink in relatively short time periods, carrying a reasonable volume of ink in the ink cartridge on the carriage has become impractical. If a small volume of ink is carried to reduce weight and momentum of the carriage, frequent change is necessary as the ink supply is rapidly diminished. Alternatively, carrying a large volume of ink in the cartridge makes the cartridge large and heavy, neither of which is desirable for a fast moving carriage.
To satisfy the goal of reducing carriage weight, and to provide adequate ink volumes for printers requiring such, it has been known to provide large volume, off carriage ink reservoirs, which are stationary in the printer. A flexible tube connects the ink reservoir to the ink cartridge on the carriage, and only a small amount of ink need be carried within the cartridge itself.
However, the use of off carriage ink reservoirs presents its own unique set of problems. It is most often necessary to operate an off carriage ink delivery system at a slight negative or back pressure, to prevent ink dripping from the nozzles. However, back pressure that is too high can result in the printhead becoming deprimed, creating additional printing problems. Further, high back pressure can draw air into the ink supply system, which then can become trapped within the ink, causing even further printing problems.
It is known to use a pump to deliver ink from the ink reservoir to the ink cartridge, and to terminate ink supply when printing ceases. A check valve in the ink supply path can be used to deliver ink to the ink cartridge only when required.
Tubing used to connect an ink reservoir to an ink cartridge typically must have very low air permeability, to prevent gas from dissolving into the ink, which can cause print defects. Such tubing is expensive and has a limited life span.
When an emptied ink reservoir is removed from the system and replaced with a fill ink reservoir, air can be introduced into the ink delivery tubing. The air can become dissolved into the ink, causing the aforementioned printing problems. If not dissolved, the trapped air will eventually enter the cartridge, and an accumulation of air in the cartridge can prematurely end the life of a cartridge by starving the printhead for ink. Additionally, long-term storage of a printer with this type of system is limited by the possibility of ink drying in the ink delivery tubing. If the ink dries in the tubing, the printer will be non-functional.
What is needed is an ink delivery system that overcomes the aforementioned problems by providing means for removing air from the system and for evacuating ink from the ink delivery tubing during periods of non-use, while being economically practical to manufacture and supply.
The present invention provides an arrangement for removing air from an ink delivery system in an ink jet printer, and for evacuating ink from the system conduit during prolonged periods of printer inactivity.
The invention comprises, in one form thereof an ink delivery system having an ink cartridge and an ink supply item remote from the ink cartridge. The ink supply item includes an ink reservoir for containing a supply of ink. An air purge chamber is in flow communication between the reservoir and the cartridge, and includes a vent with a plug of hydrophobic material in the vent, and an outlet in fluid flow communication with the cartridge. The outlet includes a check valve. A conduit connects the air purge chamber and the reservoir in fluid flow communication, for delivering ink from the reservoir to the air purge chamber.
The invention comprises, in another form thereof an air purging system for an ink delivery system having a print cartridge and a remote ink reservoir, with a pump for delivering ink from the ink reservoir to the cartridge through a conduit. The air purging system has an air purge chamber disposed in fluid flow communication between the ink reservoir and the cartridge. The air purge chamber includes an inlet connected in flow communication to receive ink from the ink reservoir; an outlet having a check valve connected in flow communication to provide ink to the cartridge; and a vent open to an ambient environment. The vent has a plug of hydrophobic material therein for readily passing air therethrough while inhibiting the passing of ink therethrough.
The invention comprises, in yet another form thereof, a method for delivery ink from a remote reservoir to an ink cartridge, comprising steps of providing an air purge chamber disposed in fluid flow communication between the reservoir and the cartridge, the air purge chamber including an inlet connected in flow communication to receive ink from the reservoir and an outlet connected in flow communication to provide ink to the cartridge; providing a vent in the chamber open to an ambient environment and a plug of hydrophobic material in the vent; pumping ink from the reservoir to the chamber in response to a demand for ink by the ink cartridge; and passing air from the chamber to the ambient environment through the vent.
An advantage of the present invention is providing an ink delivery system with an ink reservoir of high volume remote from an ink cartridge, and a system having long component life.
Another advantage is providing an ink delivery system which reduces the potential for ink to clog the system during long term storage of a printer having the ink delivery system
Yet another advantage is reducing the amount of air that will become dissolved in the ink during periods of printer inactivity, and alleviating the need for low gas permeable tubing.